Å®ÉúСÊÓƵ

A cheap and simple test that identifies skin irritants in cosmetics
and drugs could save thousands of animals from a life of suffering in laboratory
experiments.

Researchers at the Fund for the Replacement of Animals in Medical Experiments
(FRAME) in Nottingham, have just finished the first stage of development,
which draws on research showing that human skin cells produce chemicals
called cytokines when exposed to chemicals that are irritants.

Michael Garle, the project’s supervisor, says that several research
teams have tried measuring levels of cytokines as an alternative to traditional
tests where chemicals are applied to the skin of an animal such as a rabbit.
But all these groups have tried to measure levels of individual cytokines
such as specific interferons, interleukins or the tumour necrosis factor.

‘The problem with this approach,’ says Garle, ‘is that you can measure
levels of cytokines individually, but it does not give you an overall picture
of how irritating a chemical might be.’ The tests are also expensive, often
costing as much as £600 to measure one interferon.

Garle and his colleagues have designed a test that measures levels of
a chemical to show the ‘sum effect’ of all the cytokines produced by the
skin cells. This relies on the ability of macrophages, types of white blood
cell, to produce nitric oxide when they are exposed to cytokines. The nitric
oxide is used by the macrophages to destroy foreign material.

FRAME’s test relies on a standard laboratory procedure for measuring
nitric oxide called the Greiss test. When Greiss reagent – a colourless
dye – comes into contact with nitric oxide in the form of dissolved nitrite
it turns red. The deepness of the red colour reflects the amount of nitrite
present.

According to Garle, the advantages of FRAME’s test over other methods
of measuring cytokines is that each test costs only a few pence and it is
relatively simple to carry out. Skin cells are exposed to the chemical being
tested for a day. During this period cytokines will accumulate in the fluid
above the cells in amounts proportional to the irritancy of the chemical.
The fluid from the skin cell culture can then be transferred to a dish of
macrophages, which produce nitric oxide in response to the cytokines. The
Greiss test can then be used to measure the amount of nitric oxide and subsequently
the reaction of skin to the test chemical.

Advocates for Animals, a pressure group based in Edinburgh, has welcomed
FRAME’s research. Stan Blackley, its campaign officer says: ‘It will be
very attractive to industry because it will be cheaper and more relevant.
We hope it happens quickly.